There is quite a lot to digest in this particular article, but it is likely information that your pediatric cardiologist (unless specializing in WS) is unaware of.
"In conclusion, patients with WS present many peri-operative and peri-procedural challenges. A thorough pre-operative/pre-procedure screening is suggested to identify patients with anatomical abnormalities which may result in coronary artery involvement. Even with appropriate care, sudden cardiac arrest and death have been reported. Unfortunately, many of these patients are refractory to standard resuscitation protocols. Given these concerns, a thorough explanation of the risk-benefit ratio should be considered whenever diagnostic tests are considered, in patients with WS, along with a thorough discussion with parents regarding the potential risks involved."